RDMA/mlx5: Fix Q-counters query in LAG mode

Previously we used the core device associated to the IB device in order
to do the Q-counters query to the FW, but in LAG mode it is possible
that the core device isn't the one that created this VF.

Hence instead of using the core device to query the Q-counters
we use the ESW core device which is guaranteed to be that of the VF.

Fixes: d22467a7 ("RDMA/mlx5: Expand switchdev Q-counters to expose representor statistics")
Signed-off-by: Patrisious Haddad <phaddad@nvidia.com>
Reviewed-by: Mark Zhang <markzhang@nvidia.com>
Link: https://lore.kernel.org/r/778d7d7a24892348d0bdef17d2e5f9e044717e86.1685960567.git.leon@kernel.org


Signed-off-by: Leon Romanovsky <leon@kernel.org>